It’s obvious that having t’naim right before the chupah is either to give kavod to another two eidim and the reader of the document, or to fulfill the emotional need to say “We had t’naim”. Either way, it’s rather pointless. In Israel it is often skipped and no one is worse off for it.
As far as asking a shailoh if breaking an engagement is acceptable, I recommend asking the shailoh on condition that the answer will be affirmative. If one of the two parties involved don’t want to be married, then break it off. To force the marriage is stupid and evil.